The consumer market for food packaging for long-term storage has long felt a need for packaging that can be sealed for years, then opened, and then resealed for storage for additional years, without unreasonable risk of food spoilage. Available seals and methods of sealing on rigid plastic packaging do not lend themselves to long-term storage after initial opening of the package. Canned food is not re-sealable for any significant length of time after opening. Glass containers have a high breakage risk. Many ordinary plastic caps used with plastic jars and the like, are permeable to oxygen, unbeknownst to the consumer.
The present inventors encountered the skepticism of experts in developing this invention, and when they asked their commercial sealing company about the method, where told flatly that it was not possible.
U.S. Pat. No. 3,460,310 discloses a method of sealing a container opening using high-frequency induction heating of a membrane that includes a metal foil coated with a thermoplastic material. A resilient pulpboard wad (backing) is disclosed that may be releasably laminated to the foil/thermoplastic seal. Heat deformation of the pulpboard is not disclosed.
U.S. Pat. No. 4,094,460 discloses a plastic sealing ring on a container closure adapted engage the edge of the container opening, and an induction-heated metal foil/thermoplastic film for sealing to the plastic sealing ring. Customized containers and ring seals are required. Induction heating may also be used to seal the plastic sealing ring to a foil layer inside the container. body, requiring further customization of the container.
U.S. Pat. No. 5,381,913 discloses a cap having an induction seal comprising t e layers (top to bottom) of low-density polyethylene foam, wax, paper, foil, paper, wax, PET, and low-density polyethylene film. The dual releasing layers (wax) are absorbed into the adjacent paper layers upon heating. The releasing layers are not equally strong, so the aluminum foil remains on the container at first opening.
U.S. Pat. No. 5,667,089 discloses a closure with a peripheral well it the inner top surface. The inner well has integral flexible teeth which with the well compress a seal liner to wrap around the land of the container. The liner may be a heat-induction liner, which is used without a compression layer.
U.S. Pat. No. 6,082,566 discloses a re-sealable liner and induction seal made in layers (top to bottom) of support material, adhesive, foil, adhesive, polymer, adhesive, synthetic fabric, wax, thermoplastic film, adhesive, and heat sealant film and providing a transparent primary seal (the thermoplastic film, adhesive, and heat sealant film) with a resealing liner (support material, adhesive, foil, adhesive, polymer, adhesive, and synthetic fabric that has absorbed the wax). The wax is a releasing layer.
U.S. Pat. No. 6,131,754 discloses a two-piece induction seal made in layers (top to bottom) of synthetic foam, synthetic polymer, wax, metallic foil, and heat-activated polymer adhesive. The wax is a releasing layer.
U.S. Pat. No. 6,902,075 discloses a one-component tabbed seal and wadding system for a screw cap made in layers (top to bottom) of cardboard, low-density polyethylene film, a nitro-cellulose release layer, PET film, polymeric adhesive, PET tab, polyethylene foam, polymeric adhesive, aluminum foil, and hot-melt adhesive.
U.S. Pat. No. 7,217,454 discloses a tabbed seal made of layers (top to bottom) of PET film, EVA foam, a tab release strip, a release material, polyethylene foam, aluminum foil, PET film, and heat-activated sealant.
U.S. Pat. No. 7,648,764 discloses two-piece seals featuring ultrasonically welded adjacent thermoplastic film layers.
European Patent EP2013461 discloses a on-releasing seal made of layers (top to bottom) of plastics film, plastics foam adhesive, foam, foam/foil adhesive, metal foil, and heat seal. The foam and metal foil remain attached to aid recycling.
U.S. Pat. No. 5,143,763 discloses an oxygen scavenger which may be attached to the inside of a container or closure.
European Published Patent Application EP2077237 discloses a container including an EVOH layer on the inner surface and a solid desiccant attached to the interior of the container.
Patent Abstracts of Japan publication number 2000-264360 describes an oxygen-absorbing container cover including a composition of polyolefin and oxygen absorbent sandwiched between polyolefin films.
Sealing methods and materials that provide packaging impermeable to oxygen infiltration after initial sealing and after opening and re-closing are needed. A need exists for a way to scavenge oxygen inside the food container that is safe for food, and that is effective for initial packaging and after the package has been opened and then closed again.